The present invention is related to plastic articles, and, particularly, to a process of forming fiberglass articles, and, more particularly, to a process of forming the articles wherein the different layers are hand laid-up dry and the resin is placed therein from a reservoir(s) which is positioned as desired communicating through a vacuum bag.
A single rigid mold has a springy, compressible, fibrous reinforcing material, for example, placed over a prepared surface of the rigid mold part and then a relatively thin, flexible, elastic bag or envelope is sealed to the lower margins of the rigid mold. When the air is evacuated at the top, for example, from between the mold and the vacuum bag, the bag collapses against the fibrous reinforcement and forces it to follow the contours of the rigid mold. Thus it compresses the fibrous reinforcement to the minimum thickness against the surface of the mold and prevents the fibers from being displaced or washed away by the flow of the resin. Furthermore, only sufficient resin will remain in the reinforcing mat or web to adequately wet and bond the fibers and fill the voids. Under external atmospheric pressure (when the vacuum is applied internally), the bag acts as a large fluid press distributing the pressure over the entire surface of material on the mold.
The amount of resin and rate of flow through the fibrous reinforcement can be controlled by the manipulation of the vacuum. Desirably the plastic bag is transparent so that the flow of resin may be observed during the casting process.
If the article is large, the drawing of the resin up through the matrix space and through the fibrous reinforcement material causes the filaments of the fibrous material to wash or flow with the resin and as the distance of flow increases, they eventually form dams and block the flow of resin at various points. Non-homogeneous articles are thus produced.
In order to prevent such from happening, a network of veins for resin flow may be placed over the fibrous material to insure uniform filling. U.S. Pat. No. 2,913,036 is incorporated by reference.
The use of such a network adds complexity to the process and leaves possibly unwanted protrusions in the article surface where the veins are located.
For smaller articles, hand wet lay-up may be used. In this process, the catalyzed resin is firstly painted onto the mold. Then one layer of cloth (or mat) is then placed on the wet surface and it is also painted with resin. Each layer of cloth must be carefully laid on and worked to get out as many wrinkles as is possible to achieve a uniform thickness. Each layer must be saturated before the next layer is added to avoid air pockets. This process continues for as many layers as are necessary to achieve the overall desired thickness.
Excess resin must remain to allow for squeegeeing out air pockets. Thus the thickness required directly increases the time necessary for this portion of the lay-up. When all of the laminations are on and saturated with resin, a plastic bag must be sealed over them and hooked to a vacuum system. This pulls the bag tight against the wet laminations and mold. The air and excess resin can then be squeegeed out. The thicker the article's walls, the more difficult this step becomes. On larger or more complex articles this phase also requires the use of two or more journeyman level mechanics to keep a positive pace to meet gel-time requirements. If the process to this point takes longer than the gel-time, the article fails and the time and materials are wasted.
The hand wet lay-up further exposes the workers to toxic fumes and liquids and is stress prone because of the need to finish before the gel-time.
Thus there is a need for a process for non-wet hand lay-up to overcome the disadvantages of the above processes.